1. Field of the Invention
The present invention relates to a system enabling recording of a high quality image by area modulation or density modulation of each recording pixel in a dot matrix method, and is applicable to an apparatus for forming a record with ink on a recording medium such as paper, cloth or OHP sheet.
2. Related Background Art
With the recent wide spreading of office automation equipment such as personal computers and word processors, there have been developed various methods for printing the information outputted from such equipment, and, among such methods, the recording means of dot matrix recording method such as wire dot printing method, thermal transfer printing method, ink jet printing method etc. are the currently most popular digital recording systems because they are relatively inexpensive and enable space saving.
In the digital recording methods, the continuous tone is represented in pseudo manner by the covering area of plural dots on the paper, because each dot cannot be adjusted in analog manner. In recent years, however, for attaining a higher image quality, there is a strong demand for an image quality close to that of the analog recording such as the silver halide-based photography.
In such digital recording methods, it is already known that the image recording closer to the analog recording is possible by recording with multiple dots of plural kinds and by receiving multi-value data in the recording apparatus. However the handling of such multi-value data in the recording apparatus itself has not been realistic for the personal use in the recent years, because the hardware configuration required for the data transfer, RAM capacity and data development and the process time and the cost involved therein are all inevitably complex and enormous. Consequently the two-value (binary) recording in which each pixel is represented by a dot has been the mainstream of the currently employed digital recording methods.
However, based on the above-mentioned demand for the higher image quality and on the advent in the performance of the personal computers, there is being developed the multi-value recording in which each pixel is represented by plural dots. In most cases such recording is realized by a higher resolution or a reduction in size of each pixel, wherein the recording apparatus is so designed as to reproduce a higher resolution and each pixel is represented by plural dots by generating multi-value data at the preparation of the image.
FIGS. 1A and 1B show an example of the multi-value recording with plural dots. In contrast to the two-value recording shown in FIG. 1A, in which each pixel is represented by a single dot, FIG. 1B shows a multi-value recording method in which each pixel is represented by four dots. In such multi-value recording, in the image processing, information of 4 dots is generated from each pixel, and such information of 4 dots is transferred to the recording apparatus, which thus realizes the multi-value recording by a recording method identical with that in the two-value recording. More specifically, the recording of information of each bit is same as that in the two-value value recording, and four information, each binarized, are combined to constitute multi-value information.
In the example shown in FIG. 1B, the multi-value recording method is equivalent to the two-value (binary) recording method of a doubled resolution, and the information of each bit controls whether or not to print a dot. Stated otherwise, in comparison with the ordinary two-value recording method, such method is required to transfer and process the image information of four times in volume. This is because the recording apparatus lacks the function to recognize the multi-value information. Such function has been considered as complex and difficult to realize for the personal use.
However, for achieving higher image quality in the digital recording methods, it is required to realize higher reproducibility of gradation, and such requirement is anticipated to increase in the future. The major obstacle in attaining such objective lies in the time required for transfer and processing of the image information.
In the conventional systems, the image processing unit executes the multi-value process and the image information of a data amount, proportional to the number of gradation levels, is transferred to the recording apparatus. Consequently the transferred data amount becomes enormous with the improvement in the tonal rendition. Also in the recording apparatus, the capacity of the memory means, such as the print buffer for storing the information (data) of the image to be recorded, increases proportionally with the amount of the image information, and is multiplied by the number of gradation levels, in comparison with the binary recording in which each pixel is represented in two levels. Thus, such system is extremely disadvantageous in cost and this constitutes a major difficulty in realizing the personal application.
Such difficulty becomes more serious with the increase in the number of gradation levels.
For example, in comparison with the case of representing each dot with three or four levels, the representation with five or more levels by the use of inks of higher and lower densities for each dot poses a larger difficulty.
Such difficulty is not limited to the ink jet recording but is also present in other recording methods. However, the above-mentioned cost problem relating to the memory capacity or the image information transfer time is particularly difficult to resolve in the ink jet recording as it is most commonly utilized for personal applications.
An object of the present invention is to individually or entirely resolve the above-mentioned difficulties.
Another object of the present invention is to limit the amount of transfer of the image information required for image formation.
Still another object of the present invention is to limit the amount of the image information to be transferred and to enable transfer of the image data of higher tonal rendition.
The foregoing objects can be attained, according to the present invention, by an ink jet recording apparatus, an ink jet recording method, an information processing apparatus and a memory medium storing the process for controlling the functions thereof, capable of realizing a high image quality in the dot matrix recording method adapted for personal use, by limiting the amount of image information to be transferred and processed and at the same time improving the gradation reproducibility.
The foregoing objects can be attained, according to a preferred embodiment of the present invention, by an ink jet recording apparatus employing a recording head provided with plural discharge portions for discharging ink and forming a record by discharging ink from the recording head onto a recording medium according to image data, the apparatus comprising:
a mounting unit capable of interchangeably mounting a first recording head for discharging ink of relatively superior color developing ability and a second recording head for discharging ink of relatively inferior color developing ability;
image processing means for generating multi-value information from the image data; and
means for decoding the multi-value information according to the color developing ability of the ink of the recording head mounted on the mounting unit;
wherein, in the information of plural bits representing a pixel, at least a bit may have a meaning different from that of other bits.
Still another object of the present invention is to provide an information processing apparatus and a medium adapted for use with an ink jet recording apparatus of multiple functions.
Still another object of the present invention is to provide an ink jet recording apparatus capable of limiting the amount of transfer of the image information in discharging recording materials, which are of a same hue but are different in density, onto the recording medium.
Still another object of the present invention is to provide an ink jet recording apparatus with novel functions.
Still other objects of the present invention, and the features thereof, will become fully apparent from the following description of the embodiments, to be taken in conjunction with the attached drawings.